Power cables typically have at least the following three major components: (1) one or more power-transmitting conductors; (2) a sheath of electrical insulation surrounding each of the power transmitting conductors; and (3) an insulating and mechanically protective outer jacket.
Each conductor is formed of either a single strand or multiple strands of metal wire, typically copper or aluminum. The conductors are, and the cable is, flexible to a degree, and illustrative of this fact is that the cable is typically provided wound onto a reel. However, higher currents require thicker, and therefore stiffer, conductors, and higher voltages require thicker, and therefore stiffer, insulation. For transmitting large amounts of electrical power, all of the components of the power cable, including the outer jacket, are thicker and stiffer, making the cable difficult for an electrical worker to manipulate.
Aside from running or laying the power cable, the primary requirement for manipulating a power cable is to terminate it, for connecting it to a junction box, or to a load. This requires stripping away the outer jacket at the end to be terminated, to expose the conductor(s).
This operation may be explained with reference to FIGS. 1-3, which show a typical electric utility power cable referenced as 2. FIGS. 2 and 3 show the cable in cross-section. To provide an indication of scale, the cable may be 1-2 ½″ in diameter.
With particular reference to FIG. 2, the cable 2 has a central conductor 3 formed of seven strands 4 of wire. The conductor 3 is surrounded by a layer of electrical insulation 5. The insulation 5 is in turn surrounded by a support layer 6 that mechanically supports and electrically isolates from one another a number of (e.g., 10) individual conductors 7. Finally, surrounding the support layer 6, is the outer jacket, referenced as 8.
With reference to FIGS. 1 and 3, to tear the jacket a particular one of the conductors 7, e.g., the conductor 7a indicated, is selected, gripped by a gripping tool such as a pair of pliers, and pulled through the jacket 8, creating a generally longitudinally running tear-line “L.” Once the jacket is torn longitudinally, it can be cut or scored circumferentially at the desired position, such as at the position “A” indicated in FIG. 1, and removed with little additional effort.
As for the strands 4 of the conductor 3, the conductors 7 are helically or spirally wound along the cable, so that the line “L,” which is generally longitudinally running as just mentioned, tends to circle the cable as well. This circling causes a problem for the electrical utility worker. While it would take a significant effort to pull the conductor 7a through the jacket along a straight line, the fact that the line “L” tends to circle around the cable as well makes this pulling particularly awkward, because the worker's hands must also tend to circle the cable as he or she is pulling. This is particularly hard on the worker's wrists, often resulting in injuries such as carpel tunnel syndrome.
It is an objective of the present invention to minimize or eliminate this difficulty.